Lung hydroxyproline concentration after bleomycin injury. PAI-1^−/− and WT mice were treated with intratracheal bleomycin (1.15 μg/kg in 50 μL of sterile PBS) on day 0. PAI-1(V+P+), PAI-1(V+P-), and PAI-1(V-P+) were administered to subgroups of injured PAI-1^−/− animals at 100 μg/injection every 12 hours beginning on day 8 and continuing through day 19. Control groups in each of the 3 studies included bleomycin-injured PAI-1^−/− mice that received intraperitoneal PBS, bleomycin-injured WT mice that received intraperitoneal PBS, and untreated WT mice. On day 19, lung hydroxyproline levels were measured as an indicator of collagen content. Hydroxyproline results from the 3 studies were pooled and are normalized to the extent of fibrosis measured in the bleomycin treated WT group which is set at a 100% increase in lung collagen above baseline ± SEM. N = 14-26 mice per group in each study. Groups are compared with a 1-way ANOVA with Newman-Kuels posthoc multiple comparison test.